Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Sunday, November 9, 2014

SVP 2014 Day 4

Brink et al. have a poster on Bathygnathus, which I blogged about here as an ex-theropod. Turns out Case was right in 1905 that it belongs to Dimetrodon, as Brink et al. found it to be nested within that genus and sister to D. grandis. This is problematic, since Bathygnathus was named 25 years before Dimetrodon, so the ICZN will need to be petitioned if we are to retain the latter genus.

Zanno et al. present a poster on what was previously reported by Zanno (2008) as another Falcarius bonebed in the Cedar Mountain Formation of Utah, but which seems to be a more derived therizinosaur now. Originally differences were thought to be ontogenetic, but size comparisons and histology disproved this. In the new taxon, "the more prominent development of the altiliac condition of the ilium, large distal boot of the pubis measuring more than half the pubic length, relatively straight and acuminate symphyseal aspect of the dentary, reduced recurvature of the dentary teeth, and marked ventral displacement of the mandibular condyle of the quadrate appear distinct."

Larson et al. performed a morphometric analysis of Dinosaur Park coelurosaur frontals, and found that supposed therizinosaur frontal CMN 12355 grouped with Troodon, so is troodontid instead. Since Erlikosaurus wasn't included, I'm not sure how powerful this analysis is however. They say CMN 12355 "shares the following features with Troodon: a shallow lateral wall defining the fossae for the olfactory system, the exclusion of the supratemporal fossa from the dorsal surface of the frontal, and a raised orbital rim." Yet Erlikosaurus also has a shallow lateral olfactory wall (Lautenschlager et al., 2014), both therizinosaurs and troodontids are polymorphic for raised orbital rims (e.g. present in Falcarius and the Nanchao therizinosaur embryo, absent in Sinornithoides), and Troodon, Erlikosaurus and CMN 12355 all have dorsal exposure of the supratemporal fossa. They further state CMN 12355 "differs from the holotype of Erlikosaurus (IGM 100/111) in the construction of the lacrimal-frontal joint", and indeed the prefrontal-frontal articular surface in Erlikosaurus (which doesn't even have lacrimal-frontal contact) isn't exposed dorsally, unlike the contact in Troodon and CMN 12355. In comparing them myself, CMN 12355's orbital outline resembles Erlikosaurus more, but the supratemporal fossae are intermediate in their separation. Ventrally, the less anteriorly expanded olfactory bulbs and more posteriorly expanded cerebral fossae are similar to Troodon, but the prefrontal/lacrimal facet is placed far more anteromedially then in either Troodon or Erlikosaurus. So in the end I'm not convinced either way, and think CMN 12355 might belong to something else entirely. Larson et al. state "this removes the only record of a therizinosaur from the well-sampled Campanian-Maastrichtian fossil record of North America, suggesting the extinction of this group in North America prior to the Campanian,", but besides two more Dinosaur Park frontals referred to therizinosaurs by Currie (1992, 2005), there's also the pedal ungual RTMP 79.15.1 he mentions. Ryan and Russell (2001) list a cervical from the Scollard Formation of Alberta (RTMP 86.207.17), and Russell (1984) reported a therizinosaurid astragalus from the Hell Creek Formation of Montana[EDIT 2 on 2-15-15- Russell and Manabe 2002 indicate this element is actually the Tyrannosaurus quadrate initially misidentified as a quadrate by Welles and Long]. So maybe these other records are misidentified too, but there's more work to be done before we can reach Larson et al.'s conclusion.

Allain reports a new Ichthyovenator specimen which preserves "the complete cervical skeleton and the first dorsal vertebra, as well as the left pubis, seven additional caudal vertebrae and three teeth." Interestingly, "the first dorsal vertebra of Ichthyovenator is nearly identical to the holotypic vertebra of the enigmatic theropod Sigilmassasaurus brevicollis", so there's more evidence Sigilmassasaurus is Spinosaurus. "In addition to the peculiar morphology of posterior cervical and anterior dorsal vertebrae, the straight unserrated crowns of the teeth of Ichthyovenator suggest it is more closely related to Spinosaurinae than previously thought." Since my analysis including Ichthyovenator in partially corrected versions of Allain et al.'s and Carrano et al.'s matrices found it to take 0-2 more steps to be a spinosaurid than a carnosaur, and this new data provides those extra steps, I now agree the genus is spinosaurid and possibly spinosaurine.

McFeeters et al. do a rather cool thing and examine reports of ornithomimids from Foremost, Oldman and Milk River Formations of Western North America. They find pedal material from the Foremost and Oldman Formations, but the older Milk River and Foremost Formations have no definite ornithomimid material. Previously reported and catalogued material from there is indeterminate or misidentified, with "the only described specimen previously referred to Ornithomimidae" (I assume the RTMP pedal phalanx reported by Ryan and Russell in 2001the CMN pedal phalanx in plate II figure 10 of Russell, 1935) being more similarbelonging to probable Orodromeus synonym "Laosaurus" minimusa 'basal ornithopod' (so probably a thescelosaurid). The lead author notes below in a comment it is also similar to a phalanx referred to Elmisaurus though, so its identity remains uncertain for now. They suggest "the Late Cretaceous ornithomimid clade did not migrate into Laramidia until the beginning of the Late Campanian", which is possible, but I wonder just how much Foremost and Oldman material they found. After all, I'd say ~ 99% of paravian remains from these sediments are teeth, so remains of toothless taxa like ornithomimids are going to be rare by default and might not have been collected yet if the sample size is low. But if later formations preserve many thescelosaurid and ornithomimid pedal elements and earlier formations only preserve many thescelosaurid pedal elements and no ornithomimid ones, the statistical argument seems valid.

Lu et al. (misspelled as La in the abstract book) report yet another new oviraptorid from the Nanxiong Formation in addition to the prefix-triangle of Ganzhousaurus nankangensis, Nankangia jiangxiensis and Jiangxisaurus ganzhouensis, as well as the juvenile Banji long. These all actually fall out in different parts of the tree in the Lori analysis, and at least three do in the Anzu analysis, so maybe they're all valid. This new taxon is known from a partial skeletopn with incomplete skull and mandible and is "characterized by an anterodorsally sloping occiput and quadrate (shared with Citipati), a small circular supertemporal fenestra (much smaller than the lower temporal fenenstra), and the dorsal margin of the dentary above the external mandibular fenestra is strongly concave ventrally." In what I assume is a version of the Maryanska et al. analysis used in all current oviraptorosaur papers, it falls out sister to Citipati. This matches one of the named Nanxiong species in the Lori analysis, so maybe we finally have a synonymy. Might I suggest we start a new prefix-triangle and name this one 'Longia nanxiongia', then the next named species can be 'Nanxiongsaurus banjiensis'.

Button et al. have a poster on a new coelurosaur found in 2012what was originally listed as "Ornithomimidae? new genus and
species" by Kirkland et al. in 1998 from the Mussentuchit Member of the Cedar Mountain Formation of Utah. Turns out this is an "associated right hind limb consisting of a partial femoral shaft, nearly complete tibia, distal two-thirds of metatarsal IV, and pedal phalanges IV-2 and IV-4." While arctometatarsalian, "metatarsal IV most resembles Coelurus (YPM 2010) from the Upper Jurassic Morrison Formation in general proportion, mediolateral compression of the distal aspect, and near absence of a lateral collateral ligament pit, yet is unique in possessing an obliquely oriented groove marking the extensor surface and a dorsally bulbous distal condyle." Is this an ornithomimosaur, coelurid, or something else like a troodontid? Scheetz et al. had an SVP abstract in 2010 about a basal coelurosaur convergent on ornithomimosaurs from the Yellow Cat Member of this formation, but that has a non-arctometatarsalian pes, so may be unrelated. We'll have to see.

Poust et al. present the tenth supposed new Jehol microraptorian species, D2933 from the Jiufotang Formation. This "possesses several autapomorphies, including more than 29 tail vertebrae, inclined pneumatic foramina on the dorsal vertebrae, and an unusually large coracoid fenestra", and is supposedly sister to Sinornithosaurus The Cryptovolans holotype has 28-30 caudals, other Microraptor specimens often have about 26, and no complete tail is known in described Sinornithosaurus. While the Microraptor hanqingi specimen lacks inclined dorsal pleurocoels (I assume that means anterodorsally oriented), we don't know the condition in any other described microraptorian specimen. Finally, I don't know how big the supracoracoid fenestra is in D2933, but Sinornithosaurus specimens have fenestrae varying in size between 27 and 35 percent of coracoid height. Poust et al. state "all visible neurocentral sutures, and proximal tarsals remain unfused. The porous surface texture of the cortical bone and poor ossification of long bone articular surfaces further supports an immature status. Histologic samples of the tibia, fibula, and humerus confirm that it was about one year old and still growing at death." As D2933 is smaller than Sinornithosaurus, differences could be ontogenetic, and indeed increased ossification with age could shrink the supracoracoid fenestra's size. It has "filamentous feathers, pennaceous feathers extending from the fore- and hindlimbs, and two long plumes extending more than 12 cm beyond the caudal series", which the authors contrast with Sinornithosaurus that shows "only branching filamentous feathers." They propose "that this simplified condition is a secondary loss of feathers, either as a feature of the genus [Sinornithosaurus], or as part of an ontogenetic loss of 'advanced' feather types in adults." Or maybe it's taphonomic, as described Sinornithosaurus specimens are disarticulated. Much as with Lefevre et al.'s talk, I think we need a Lagerstatten rule for dinosaurs- 'Do not ascribe to phylogeny that which can be explained by taphonomy'.

Kobayashi et al. present a poster on what I assume is a specimen of "Gallimimus" mongoliensis that's basically identical to their 2007 SVP abstract, so I hope we see this taxon published soon.

Gerke and Wings have an interesting study of Late Jurassic German theropod teeth. "Four Langenberg Quarry teeth, previously assigned to velociraptorine dinosaurs, are removed from Dromaeosauridae and regarded as belonging to Tyrannosauroidea, Neotheropoda and Megalosauridae based on their dental characters." Maybe their DFA analysis could be used to classify other supposed dromaeosaur teeth that plague studies depending on Dinosaur Park morphologies.

Malafaia et al. present information on a new Lourinha megalosauroid specimen represented by "several cranial fragments including an incomplete left maxilla." Several characters differ from Torvosaurus, known there from T. gurneyi. So this may be Lourinhanosaurus, which is coelurosaurian in Carrano et al.'s tetanurine matrix partly due to miscoding it as lacking a pubic obturator fenestra.

Velocipes guerichi holotype proximal fibula in a (lateral), b (posterior), c (medial) and d (anterior) views, with proximal view on top and cross sections at right (after Huene, 1932).

Czepinski et al. had a poster on Triassic dinosaurs from Poland, which is one of my favorite kinds of papers- reevaluating historical taxa. Middle Triassic supposed dinosaurs can't even be referred to Dinosauromorpha, but "new analysis of the Velocipes guerichi holotype from Kocury site (Silesia) suggests that it is probably the proximal part of an elongated and flattened fibula of a neotheropod dinosaur." So Huene was right 80 years ago, whereas Rauhut and Hungerbuhler (2000) listed it as Vertebrata indet.?! Because it was plausibly a fish? One negative effect of cladistics is that some authors (Nesbitt et al., 2007 *cough*) only use characters coded in an analysis to classify specimens, when plenty of other differences exist between clades. I'm glad Czepinski et al. didn't follow this method. Now we just need a good reexamination of Avipes, Dolichosuchus and Halticosaurus.

That's it for SVP 2014. Hope you enjoyed my theropod rundown.

Edit: Thanks to Brad McFeeters for correcting some of the information here, with the corrected info bolded above and the original wrong text crossed out. It's like peer review for blogs. :)

8 comments:

Aw, you should have been there. :-( Are you coming to Dallas next year?

LOL @ prefix triangle.

This is problematic, since Bathygnathus was named 25 years before Dimetrodon, so the ICZN will need to be petitioned if we are to retain the latter genus.

Indeed; the poster says so.

Zanno et al. present a poster on what was previously reported by Zanno (2008) as another Falcarius bonebed in the Cedar Mountain Formation of Utah, but which seems to be a more derived therizinosaur now. Originally differences were thought to be ontogenetic, but size comparisons and histology disproved this.

The poster also made clear that the new taxon is eerily troodontid-like.

Because it was plausibly a fish?

That possibility, assuming it counts as a possibility, was not mentioned on the poster...

I knew Bathygnathus was going to go through this eventually... and I've got mixed feelings (thought note all personal and not scientific). Being from Prince Edward Island, it still baffles me that anyone could find any large vertebrate remains here (the island is essentially made of sandstone - literally). Now, it being sunk (er... petitioned), I can now say a reasonably well known and popular prehistoric animal is found here (because most know no difference in species for such creatures), but on the other hand Bathygnathus was the one unique thing found here. But I digress. Does show how nomenclature opinions can differ form person to person in unique ways, thought.

As for actual implications, I believe this is one of the largest Dimetrodon species, right? Also, there's the fact that it's found this far North. Sure, there's the German species, but otherwise it's known from the South U.S.. Then there's the geology of the island I mention earlier: Almost entirely red sandstone. It's unlikely any more fossils of the species will ever be found, and if any are, it'll be very fragmentary.

Yeah, I can see how losing the uniqueness of Bathygnathus would be disappointing. "Just another Dimetrodon?! The world has tons of those." I'm not sure how Dimetrodon species differ in size or distribution, as I have very little literature on them. As for more Bathygnathus specimens, "ever" is a long time, and there are red sandstones with lots of specimens once we search them, like the Navajo Sandstone, right? I figure it's just that there haven't been any/many paleontological expeditions to the island.

I see little value in reporting on abstracts for a conference that one did not attend. When abstracts are hastily written half a year in advance, and not formally peer-reviewed, they can end up misrepresenting the conclusions of the eventual poster (or even further down the road, the paper) and should be taken with a grain of salt. In the case of my poster, we did not refer the published Milk River "ornithomimid" phalanx (in fact a CMN specimen figured in L. S. Russell, 1935) to Ornithopoda or Thescelosauridae. We simply figured a phalanx from "Laosaurus minimus" (has this been officially recovered as a thescelosaurid yet?) as one of several dinosaur phalanges that the Milk River specimen had more in common with than Ornithomimidae. That's all. The Milk River phalanx is also very similar to a phalanx referred to Elmisaurus from Montana (I noticed the closeness of this resemblance slightly after the abstract deadline, unfortunately), so it may still be a coelurosaur. Maybe it's actually a pedal element of Richardoestesia. I don't know, I'm still working on the paper. We did not report any definitive ornithomimid material from the Foremost Formation in either the abstract or the poster. No argument from statistics was presented, so I agree with your concerns about the absence of evidence, but that line of the abstract about the Milk River and Foremost being well-sampled came from my coauthors who have done lots of fieldwork in those formations.

Button's poster wasn't about the material listed by Kirkland et al. in 1998, it was about a new specimen collected in 2012.

An intriguing note on Zanno's poster was that since the new troodontid-like therizinosaur comes from the same locality as the holotype of Geminiraptor suarezarum, and no other troodontid material has been found, could Geminiraptor actually be a therizinosaur? Not presently really testable, beyond the phylogenetic analyses that have already recovered it as a troodontid, but something interesting to speculate about.

Lü's new oviraptorid poster was sadly never presented, if I recall correctly (and I really hope I do, since my poster was to be in the same row and session). I don't think I saw him at the conference at all.

Hi Brad. One value to these blog posts is informing people of cool things from SVP who didn't want to slog through the abstract book. You're helping with another value- informing us all of details not included in the abstracts. These abstracts are going to be out there forever after all, so if parts are confusing or have changed since submission time, it's good to get that info out. I do hope some of the SVP discussion happening on vrtpaleo this month results in later abstract deadlines for future years though.

Good to know that the phalanx isn't necessarily an ornithopod. I suppose you did say it "more closely resembles a pedal phalanx from a small, gracile-footed basal ornithopod" as opposed to explicitly saying it was an ornithopod, but you gotta admit the former phrasing is often used by authors to indicate the latter conclusion. As for "Laosaurus" minimus, Scheetz (1999) thought it was probably referrable to Orodromeus and notes it has a laterally flat greater trochanter, which is a thescelosaurid synapomorphy in Brown et al. (2014). I just figured since all Campanian-Maastrichtian North American hypsilophodont-grade ornithopods analyzed so far are thescelosaurids, any fragments are likely to be so too. The Foremost Formation thing was my goof in misreading the abstract. Thanks for informing me about Russell (1935), as I didn't have that paper yet.

Interesting that Button et al.'s specimen is different than Kirkland et al.'s. I'm looking forward to the descriptions of all of these North American basal coelurosaury things, and Nedcolbertia could use a redescription too.

Funnily enough, Geminiraptor never emerges as a troodontid in the Lori analysis.

I don't think Ichthyovenator's hindlimb length has any bearing on Spinosaurus'. A short hindlimb would be a derived character, so could have evolved anywhere between Baryonychinae and Spinosaurus. It would be interesting to know how MN 4819-V compares, a partial postcranium from the Santana Formation that is probably Irritator. For the record, I think Ibrahim et al. are probably correct that the neotype is one individual with a short hindlimb, but agree with Cau that they really botched things by proposing the idea without releasing the 3D model demonstrating this to the public.